Rotary stepper actuators or motors wherein an output shaft thereof is rotated in discrete steps in response to one or more sensed input signals are well known in the art of control mechanisms and have taken various forms as, for example, the pneumatically operated nutating motor of U.S. Pat. No. 3,486,518 and the electrically operated nutating motor of U.S. Pat. No. 3,322,984. Such prior art nutating or stepper motors are not entirely satisfactory for use in certain operational environments wherein size, weight, system complexity, resistance to heat and/or vibration and reliability are of prime concern. The present invention represents an improvement over such prior art stepper actuators or motors in that it provides a relatively structurally simple, compact, reliable stepper motor which is highly resistant to adverse effects created by excessive heat and/or vibration, and capable of high power output.